When ./test_xdp_vlan_mode_generic.sh runs it complains that it can't
find file test_xdp_vlan.sh.
# selftests: bpf: test_xdp_vlan_mode_generic.sh
# ./test_xdp_vlan_mode_generic.sh: line 9: ./test_xdp_vlan.sh: No such
file or directory
Rework so that test_xdp_vlan.sh gets installed, added to the variable
TEST_PROGS_EXTENDED.
Fixes: d35661fcf95d ("selftests/bpf: add wrapper scripts for test_xdp_vlan.sh")
Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>